The invention relates to the art of map making. Geographic information is available in a variety of forms, and numerous Geographic Information Systems (GIS) have been implemented and are used throughout the world. These information systems allow organizations to display, manipulate and analyze geographical data.
The United States Geological Survey (USGS) is one of the major sources of raw geographical data at the present time. USGS transforms a hard copy of a map into a digital form. This is called a digital map. The digital data is stored on tape and sold to users in an ASCII format known as digital line graph (DLG) format (defined by USGS as Digital Line Graphs from 1:100,000 Scale Maps by the Data User Guide 2, available from USGS). This data is in a vector format. USGS provides DLG tapes on various topographical coverages including hydrology, roads, railroads, and miscellaneous transportation. Miscellaneous transportation may include data such as power lines, pipes, air strips, ski lifts, tramways and the like.
USGS provides DLG data blocks in map sections which cover a 7.5 minute by 7.5 minute area of the earth's surface (7.5 minute map). This area is equivalent to one-eighth of a degree longitude by one-eighth of a degree latitude. The area encompassed by a 7.5 minute map varies, depending upon the location on the earth's surface. Within the Continental United States, the area is typically about 10-11 km east to west by about 19 km north to south. More than 50,000 of USGS's 7.5 minute maps are required to completely cover the Continental United States (CONUS) for each type of coverage (i.e. 50,000 maps for roads, 50,000 maps for railroads, etc.). As a further example, the State of Kentucky requires 765 of the 7.5 minute maps to completely cover its borders.
It is often desirable to have a single map which covers a larger area than the 7.5 minute map. Also, it is often necessary to create a map which includes more than one topographical feature, for example, a map with both roads and railroads may be desired.
The Environmental Science Research Institute (ESRI) has developed a software package called ARC/INFO which is used for processing the data from DLG files. The DLG data files are not directly compatible with the ARC/INFO system. Before ARC/INFO can be used, the DLG data files must be converted into ARC/INFO format.
ARC/INFO includes a program which allows the user to convert the raw DLG data files into ARC/INFO format. This conversion program requires periodic human interfacing with the program. Thus an operator must be present throughout the conversion process to input the proper parameters to the computer at various stages in the conversion. The operator loads the tape, and the program prompts the operator for additional information. The system prompts the user for the DLG file name, the number of files to process and the name of the directory in which to store the data in. This is a long, time consuming operation which is subject to error because of the constant human interaction.
The second step in producing a larger map from the 7.5 minute map sections is an edgematching procedure, wherein the edge features of one map are matched to the corresponding features on the four surrounding maps. This process is completed in the prior art systems by a manual edgematching process. This process will be described in more detail below.
As shown in FIG. 1, a larger map 10 is often desired as opposed to the individual 7.5 minute maps 12. An enlarged version of the 7.5 minute map labelled A is shown in FIG. 2. Map A is shown to contain various arcs which represent topographical features (i.e. roads, waterways, etc.). It will be appreciated by those skilled in the art that an actual 7.5 minute map may contain hundreds or even thousands of these arcs.
As mentioned above, the edgematching process of the prior art systems requires a manual edgematching step. To match the edges, the two adjacent data sets representing the edges to be matched are called up onto a computer screen. The computer screen typically places these edges approximately one inch apart. For every node along an edge (16 and 26, for example), the operator must locate the corresponding node on the adjacent data set. The operator selects the end node of one of the edges, looks over at the adjacent edge,.makes an interpretation of which feature on this edge he believes that the first end node should be joined to, and he selects this feature. The operator then enters a command on his keyboard that joins these two features together. This is called "snapping" the two features together. This manual matching process must be performed on every node along the edge, along every edge on the 7.5 minute map, and around every map that is to be joined. As mentioned above, there are more than 50,000 7.5 minute maps per coverage (i.e. hydrology, roads, etc.) to cover the Continental United States.
Those skilled in the art recognize the time consuming and tedious nature of this edgematching procedure. Furthermore, matching of every node requires a judgment on the part of the operator; hence, this process is highly error prone. The operators become tired and bored, nodes are completely missed, mismatched, and many other human errors may be involved. It is also a very time consuming process; therefore, it is also very costly in terms of man hours and money. Additionally, this process requires a graphic terminal to match the edges on.
Furthermore, the final product is also full of errors. It is virtually impossible to obtain an error free final map product.
The final steps in creating the map product are to correct the attribute files and to clean up any coverage which does not have the correct topology. Then, the various individual coverages (7.5 minute maps) desired in the final product are combined into a single map layer.
In the prior ar& systems, the user again was required to manually interface with the computer, this time to assure that the attribute files for each map matched up. The attribute file of each individual file (7.5 minute data file) had to be looked at individually to determine how many attributes were missing. The correct number of attributes cannot be determined until all of the files are inspected. After inspecting all of the attribute files, the operator then needed to determine the correct number of attributes, and enter any missing attributes into each individual file by means of a program routine called ADDITEM. ADDITEM is a routine that is a standard command in the ARC/INFO package which allows the user to enter attributes. The operator is required to enter the ADDITEM command over and over on the terminal. This process is also extremely time consuming and tedious.
The procedure for joining the individual maps into a single coverage was relatively simple for the user in the prior art systems. The user only needed to enter all of the individual file names for the maps that were to be joined. ARC/INFO would join these files into one map layer. This is also a very tedious chore in situations where hundreds or thousands of individual data files are being joined.
As noted above, the process of the prior art requires a large investment of time and money. Shown in Table I are the approximate times requires to process 256 DLS files using the prior art manual processing methods.
TABLE I ______________________________________ Process Time ______________________________________ 1. Convert DLG files into ARC/INFO, 100 man hours building topology, projecting, reading tapes, etc. 2. Edgematching (correcting map 100 man hours features to meet at the map borders). 3. Attribute correction and combining 32 man hours of individual maps into a single layer. TOTAL 232 man hours ______________________________________
Since this data is processed manually, there are typically numerous errors which are present in the processed data.